Automatic-reclosing should not be attempted when closing a CB and energizing a line
onto a fault (SOTF), except when multiple-shots are used where shots 2 etc. will be
started at SOTF. Likewise a CB in a multi-breaker bus bar arrangement which was not
closed when a fault occurred should not be closed by operation of the Auto-Reclosing
function. Auto-Reclosing is often combined with a release condition from
synchrocheck and dead line or dead bus bar check. In order to limit the stress on turbo-
generator sets from Auto-Reclosing onto a permanent fault, one can arrange to
combine Auto-Reclosing with a synchrocheck on line terminals close to such power
stations and attempt energizing from the side furthest away from the power station and
perform the synchrocheck at the local end if the energizing was successful.
Transmission protection systems are usually sub-divided and provided with two
redundant protection IEDs. In such systems it is common to provide auto-reclosing in
only one of the sub-systems as the requirement is for fault clearance and a failure to
reclose because of the auto-recloser being out of service is not considered a major
disturbance. If two auto-reclosers are provided on the same breaker, the application
must be carefully checked and normally one must be the master and be connected to
inhibit the other auto-recloser if it has started. This inhibit can, for example, be done
from STBRREC (79) In progress.
When Single and/or three phase auto-reclosing is used there are a number of cases
where the tripping shall be three phase anyway. Some examples are:
When Single and/or three phase auto-reclosing is used there are a number of cases
where the tripping shall be three phase anyway. Some examples are:
• Evolving fault where the fault during the dead-time spreads to another phase. The
other two phases must then be tripped and a three phase dead-time and
autoreclose initiated
• Permanent fault
• Fault during three phase dead-time
• Auto-reclose out of service or CB not ready for an auto-reclosing cycle
Prepare three phase tripping is then used to switch the tripping to three phase. This
signal is generated by the auto-recloser and connected to the trip function block and
also connected outside the IED through IO when a common auto-recloser is provided
for two sub-systems. An alternative signal Prepare 1 Phase trippingis also provided
and can be used as an alternative when the autorecloser is shared with another
subsystem. This provides a fail safe connection so that even a failure in the IED with
the auto-recloser will mean that the other sub-system will start a three-phase trip.
A permanent fault will cause the line protection to trip again when it recloses in an
attempt to clear the fault.
The auto-reclosing function allows a number of parameters to be adjusted.
Examples:
Section 10 1MRK 505 291-UEN A
Control
214
Application manual
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